Dipartimento di Ingegneria Chimica Materiali Ambiente, Sapienza Università di Roma, Via Eudossiana 18, Roma 00184, Italy.
Anal Chem. 2021 May 4;93(17):6808-6816. doi: 10.1021/acs.analchem.1c00780. Epub 2021 Apr 23.
Microcapillary hydrodynamic chromatography (MHDC) is a well-established technique for the size-based separation of suspensions and colloids, where the characteristic size of the dispersed phase ranges from tens of nanometers to micrometers. It is based on hindrance effects which prevent relatively large particles from experiencing the low velocity region near the walls of a pressure-driven laminar flow through an empty microchannel. An improved device design is here proposed, where the relative extent of the low velocity region is made tunable by exploiting a two-channel annular geometry. The geometry is designed so that the core and the annular channel are characterized by different average flow velocities when subject to one and the same pressure drop. The channels communicate through openings of assigned cut-off length, say . As they move downstream the channel, particles of size bigger than are confined to the core region, whereas smaller particles can diffuse through the openings and spread throughout the entire cross section, therein attaining a spatially uniform distribution. By using a classical excluded-volume approach for modeling particle transport, we perform Lagrangian-stochastic simulations of particle dynamics and compare the separation performance of the two-channel and the standard (single-channel) MHDC. Results suggest that a quantitative (up to thirtyfold) performance enhancement can be obtained at operating conditions and values of the transport parameters commonly encountered in practical implementations of MHDC. The separation principle can readily be extended to a multistage geometry when the efficient fractionation of an arbitrary size distribution of the suspension is sought.
微流控毛细电泳（MHDC）是一种成熟的技术，用于基于尺寸的悬浮液和胶体分离，其中分散相的特征尺寸范围从几十纳米到几微米。它基于阻碍效应，防止相对较大的颗粒经历压力驱动层流通过空微通道时壁附近的低速区。这里提出了一种改进的设备设计，其中通过利用双通道环形几何形状使低速区的相对程度可调。该几何形状设计使得在相同的压降下，核心和环形通道具有不同的平均流速。通道通过指定截止长度的开口进行通信，例如 。随着它们在通道中向下游移动，尺寸大于 的颗粒被限制在核心区域，而较小的颗粒可以通过开口扩散并分布在整个横截面，从而实现空间均匀分布。通过使用经典的排除体积方法对颗粒输运进行建模，我们对颗粒动力学进行了拉格朗日随机模拟，并比较了双通道和标准（单通道）MHDC 的分离性能。结果表明，在 MHDC 实际应用中常见的操作条件和输运参数值下，可以获得定量的（高达三十倍）性能提升。当需要对悬浮液的任意尺寸分布进行有效分级时，分离原理可以很容易地扩展到多阶段几何形状。
